ASP.NET Core (VI) DI manually obtains the method of injecting objects

Little scum · Posted on 2021-3-19 15:13:15

Tutorial on ASP.NET Core Dependency Injection, Control Inversion (DI IOC):

ASP.NET Core dependency injection uses the IOC container that comes with it
https://www.itsvse.com/thread-7562-1-1.html

Review:

ASP.NET Core (five) is based on CAP distributed transactions
https://www.itsvse.com/thread-9593-1-1.html

ASP.NET Core(4) filter unified ModelState model validation
https://www.itsvse.com/thread-9589-1-1.html

ASP.NET Core (iii) Dynamically create instances using ActivatorUtilities
https://www.itsvse.com/thread-9488-1-1.html

ASP.NET Core (2) Restart the application by code
https://www.itsvse.com/thread-9480-1-1.html

ASP.NET Core (1) uses Redis caching
https://www.itsvse.com/thread-9393-1-1.html

Dependency injection in a nutshell:

Dependency injection (DI) is a technique that implements loose coupling between an object and its collaborators or dependencies. Provide these objects that the class uses to perform its operations to the class in some way, rather than directly instantiating collaborators or using static references.

ASP.NET Core DI generally uses constructor injection to obtain objects, such as after configuring the ConfigureServices injection, it can be obtained in the following ways:

Login is visible.

What if you manually get the injection object?

The first way to get it(Sometimes you can't get it,Not recommended）：

Login is visible.

The second way to get it（Recommended use）：

Login is visible.

Note: It should be noted that using ServiceLocator.Instance.GetService<T>(); ，Only objects injected by AddTransient and AddSingleton can be fetched, and cannot obtain the injected object of AddScoped (unique in the request lifecycle), not because it cannot be obtained, but because the acquired object is not obtained by the constructor, that is, the acquired object is not shared, and the usage scenario is such as IUnitOfWork.

So how do you manually get the injection objects during the request lifecycle? Here's how:

Login is visible.

or

Login is visible.

The IHttpContextAccessor interface is under the Microsoft.AspNetCore.Http.AbstractionsNuget package.